Conventional high bandwidth or broadband amplifiers include single path and multi-path designs. Generally, the multi-path designs are dual path architectures. A dual path amplifier is typically designed to split frequency response into two bands via a low bandwidth path and a high bandwidth path. The low bandwidth path covers from DC up to a crossover frequency (fco) and the high bandwidth (or broadband) path covers from the crossover frequency fco to the maximum bandwidth of the amplifier. The low bandwidth path typically provides less than about one percent of the total bandwidth of the dual-path receiver. Amplifiers employing this technique may be sufficient in some cases, but they do not achieve as high of frequency band edges as narrowband amplifiers used in wireless communications applications, known as a low noise amplifier (LNA).
Also, a drawback of conventional single path DC coupled amplifiers is that they require several support circuits to work properly, including circuits for gain adjustment, thermal compensation, level translation, and cascading of stages, for example. These support circuits, along with biasing circuits, slow down the DC coupled amplifiers. In comparison, support circuits are either not needed or simplified in LNAs.